A method and arrangement of this kind are disclosed, for example, in U.S. Pat. Nos. 5,031,595 and 5,046,467.
U.S. Pat. No. 5,046,467 discloses a control system for adjusting the throttle flap in idle for idle control. For this purpose, a positioning device is provided which actuates a contact when the throttle flap comes into contact engagement with a movable stop whereafter the idle control is activated. In normal driving operation, and when the throttle flap is lifted away from this stop by actuating the accelerator pedal, the stop is moved to a predetermined position which lies above the throttle flap angle necessary for idle control. The stop is moved to the position necessary to idle control in accordance with a pregiven time function when the throttle flap comes into contact engagement with this stop. This so-called dashpot function improves the exhaust gas performance and the driving performance when the accelerator pedal is suddenly released and effectively prevents undershoots in the speed of the engine.
The above arrangement is problematic in that no position feedback with respect to the stop is provided during driving operation. For this reason, the danger is present that the stop is moved too little or too far in the open direction of the throttle flap during driving operation so that an unwanted high idle engine speed can occur when the throttle flap is in contact engagement with the stop or an engine speed which is too low can occur which can cause the engine to stall.
Problems of this kind are present in those control systems for positioning devices wherein no position feedback of the positioning element is provided. This is also, for example, the case for simple drive slip-control systems without position feedback of the throttle flap for which the actuation of the throttle flap in the direction of the closed position leads to a reduction of the slip and leads to a stalling of the engine in an unfavorable situation.